The present invention relates to an improved riser for an irrigation sprinkler system and, in particular, to a retractable sprinkler wherein, said riser is biased in a normally retracted position, and, upon the introduction of fluid, said riser rises to consequently dissipate said fluid.
Prior art irrigation sprinklers embody a wide variety of different functional mechanisms. There are two major sprinkler systems of the inground type which include a housing which is buried just below ground surface, wherein a riser is biased in a normally retracted position such that upon the introduction of fluid, the riser rises to an elevated sprinkling position.
One type of known inground irrigation sprinkler system comprises sliding fluid riser tubes. Generally this type of sprinkler system does not allow good extension between a retracted position and an elevated position. Consequently, the sprinkler does not produce good water distribution. Further, the sprinkler riser tends to stick within the sliding riser guide, due to grass, soil or other material, which is added to the soil in granular form for the purposes of fertilizing insect or weed control, becoming lodged within the housing. These prior art sprinklers therefor require continual and extensive maintenance in removing this matter from the sliding parts of said riser guides.
In order to overcome the disadvantages of the aforementioned type of inground irrigation sprinkler systems, it has also been previously proposed to provide a flexible diaphragm suspended between the housing wall and the riser tube. Such a diaphragm serves the dual purpose of providing a seal between the housing wall and the riser tube such that foreign matter is prevented from entering the sprinkler, and, also acts to provide the support for the riser and its movement between the retracted and the elevated sprinkling position. These diaphragm type arrangements do offer some advantages, however, the prior art sprinkler systems utilizing this type of mechanism all have a number of shortcomings.
In order to provide a diaphragm-type sprinkler arrangement which allows sufficient movement and also ensures automatic retraction of the riser upon impedance of the fluid flow, it was proposed to employ springs, which would retract the riser whilst not in use. A number of various embodiments of diaphragm-spring arrangements have been proposed utilizing tension-spring arrangements, however, due to the design of such risers, it has not been possible to produce a compact sprinkler unit. A tension spring cannot extend elastically to more than roughly twice its relaxed length. Therefore, in order to provide good extension of the riser, a spring of considerable length is necessary. However, longer springs result in a less compact sprinkler unit. Therefore, the tension springs employed must be selected such that they have sufficient force to effect and maintain retraction, and such that they do not restrict the movement of the riser from reaching a good extended position. In order to effect a good sprinkler-unit design, it has therefore been necessary to compromise between large vertical extension and diaphragm positioning.
The vertical movement of the diaphragm arrangement can be minimized if the diaphragm is attached to the housing at a level corresponding with the base of the sprinkler head. The disadvantage of this arrangement is that debris can collect in the space provided for it which will inevitably lead to interference with the operation of the sprinkler head.
If the diaphragm is attached as closely as possible to the top of the housing, then the vertical distance that the sprinkler head travels is necessarily a function of the need for retracted containment of the sprinkler head and the depth of the conical shaped diaphragm.
U.S. Pat. No. 2,901,183 in the name of G. C. KOHL, discloses a typical diaphragm-spring arrangement displaying many of the above-mentioned shortcomings. Kohl's sprinkler comprises a housing provided with a diaphragm at the top thereof. The sprinkler head is provided in the center of the diaphragm, and a spring is fixed therebelow to the bottom of the housing. Kohl's sprinkler however has a number of drawbacks. Firstly, due to the construction of the sprinkler, the device is reasonably difficult and expensive to manufacture, and difficult to assemble and install ready for use. According to Kohl's design having a top mounted diaphragm controlled by a tension spring arrangement and incorporating sufficient sprinkler head rise and retraction to accommodate a compact sprinkler, such an implementation would require a housing diameter to length ratio of about 1:4. For example a common golf course pop-up riser with a 20 cm diameter housing would require an 80 cm housing length, which is impractical because of the depth of the hole required to house it, the depth of the piping of the reticulation system and the high frequency of shallow soil depths occurring where sprinkler systems are typically installed. Once assembled, a number of inherent problems become obvious during the functional operation of the sprinkler. The expansion spring arrangement employed by Kohl does not offer sufficient force and direction of force to hold the riser in a vertical position when extended. Since the spring is merely connected to a hook provided underneath the center of the sprinkler head, and due to the turbulance of the water within the chamber, the sprinkler head is unlikely to be maintained in a vertical position, but rather, would tend to wobble and rotate from its correct position. Thus, the fluid would then not dissipate evenly from the sprinkler head. Further, due to this resultant movement on the spring, the spring tends to become twisted, etc., and consequently, fatigue takes place which affects the correct operation of the spring. Eventually, the spring could become distorted and stretched, and may not retract the sprinkler head back into the housing.
The present invention seeks to provide a retractable sprinkler system which overcomes the disadvantages of the herein-above mentioned prior art sprinklers.
The present invention seeks to provide a compact sprinkler which is constructed of minimal parts and which is of compact design.
The present invention seeks to provide a sprinkler system which is provided with a diaphragm, which prevents any foreign matter from reaching the housing of the sprinkler.
The present invention also seeks to provide a sprinkler system in which the riser undergoes smooth movement between the retracted position and the elevated position, which allows large vertical extension, and which retains the sprinkler head in a substantially vertical position during use.